Question

After self-pollination in pea plants with round, yellow seeds. Following types of seeds were obtained by Mendel: Round-Yellow- 630, Round-Green - 216, Wrinkled- Yellow -202, Wrinkled- Green - 64. Analyze the result and describe the mechanism of inheritance which explains these results.

Answer 1

Seeds	Round, Yellow	Round, Green	Wrinkled, Yellow	Wrinkled, Green
Number	630	216	202	64

1. The ratio obtained is 9:3:3:1 in which the parental as well as new combinations, can be seen.
2. This shows that progeny plants did not inherited a single complete gene set from each parent.
3. Every germ cell takes one chromosome from the pair of maternal and paternal chromosomes.
4. When two germ cells combine, the segregation of one pair of characters is independent of another pair of characters.

Dihybrid cross:

1. A dihybrid cross describes a mating experiment between two organisms that are identically hybrid for two traits.
2. A hybrid organism is one that is heterozygous, which means that carries two different alleles at a particular genetic position or locus.
3. In a dihybrid cross, Mendel took a pair of contradicting traits together for crossing; for example color and the shape of seeds at a time.
4. He picked the wrinkled-green seed and round-yellow seed and crossed them.
5. He obtained only round-yellow seeds in the F1 generation. This indicated that round shape and yellow color of seeds are dominant in nature.
6. While the wrinkled shape and green color of seeds are recessive traits.
7. Then, F1 progeny was self-pollinated.
8. This resulted in four different combinations of seeds in F2 generation.
9. They were wrinkled-yellow, round-yellow, wrinkled-green seeds and round-green in the phenotypic ratio of 9:3:3:1.